Adds `py_require()` function #1357

Job	Run time
OS=macOS-latest R=release py=3.11	3m 51s
OS=windows-latest R=release py=3.11	8m 42s
OS=ubuntu-latest R=release py=3.11	4m 44s
OS=macOS-latest R=oldrel py=3.11	3m 53s
OS=ubuntu-latest R=oldrel-1 py=3.10	4m 52s
OS=ubuntu-latest R=oldrel-2 py=3.10	5m 28s
OS=ubuntu-20.04 R=oldrel-3 py=3.9	5m 0s
OS=ubuntu-20.04 R=oldrel-4 py=3.9	4m 47s
OS=ubuntu-latest R=release py=3.8	4m 58s
OS=ubuntu-latest R=release py=3.9	4m 17s
OS=ubuntu-latest R=release py=3.11	5m 53s
OS=ubuntu-latest R=release py=3.12	2m 44s
OS=ubuntu-latest R=release py=3.13	7m 38s
OS=ubuntu-latest R=devel py=3.13	6m 11s
	1h 12m 58s

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